Photo-offset plate making machine

ABSTRACT

A photo-offset platemaking machine, including a negative carrier selectively positioned in fixed position upon a frame or base, and a negative carrier illumination device including a housing having an opening corresponding in size and shape to a planar surface on the negative carrier. The housing includes a source of illumination, and continuous light proof venting members periferally arranged on said housing adjacent said opening, whereby when the continuous edge defining the opening is placed in abutted relation with respect to the planar surface of the negative carrier, a light-tight seal is effected, and air is drawn through the ventilating members to form a cushion of air over the negative carrier to protect the negative from the heat of the illumination device. A cooling element exhausts the air from the hood at a point remote from the opening.

United States Patent Division of Ser. No. 537,464, Mar. 25, 1966, Pat.No. 3,484,166.

PHOTO-OFFSET PLATE MAKING MACHINE 1 Claim, 8 Drawing Figs.

2,317,691 4/1943 Morin 3,033,980 5/1962 Pickeringetal.

ABSTRACT: A photo-offset platemaking machine, including a negativecarrier selectively positioned in fixed position upon a frame or base,and a negative carrier illumination device including a housing having anopening corresponding in size and shape to a planar surface on thenegative carrier. The housing includes a source of illumination, andcontinuous light proof 1.8- CI. venting member perife -ally arranged onsaid housing ad.

- 240/ 47 jacent said opening, whereby when the continuous edgedefinlnt. Cl G03b 27/52 ing the Opening is placed in abuued relationwith respect to Field of Search 355/30, 67, the planar surface f thenegative carrier, a lighmight sea] is 1 13; 240/47 effected, and air isdrawn through the ventilating members to R I cud form a cushion of airover the negative carrier to protect the e negative from the heat of theillumination device. A cooling UNITED STATES PATENTS element exhauststhe air from the hood at a point remote from 2,242,525 S/l94l Kirlin240/47 the opening.

' A22 A3 I /36 4?] i E K77 s C g $457 I I r 1 Z i i I I I ,32 f2! 1 /3/PHOTO-OFFSET PLATE MAKING MACHINE This application is a division ofapplication Ser. No. 537,464, filed Mar. 25, 1966, now U.S. Pat. No.3,484,166.

This invention relates generally to the plate-making art used inphoto-offset lithography printing and more particularly to a machineparticularly adapted for multiplate printing and color work. Referenceis made to my prior US. Pat. No. 3,150,582, granted Sept. 24, 1964, thepresent invention relating to improvements in structure disclosedtherein. i

In the photolithographic process, it is frequently desirable to havemultiple images in spaced and predetermined positions on thephotographic plate, which images are obtained by repetitive exposure.Certain economies result from the production of a number of identicalreproductions from a single plate impression, and in color work thenumber of impressions is equal to the number of colors used. In order toreproduce work of highly acceptable quality, it is necessary that thevarious color impressions be exactly superimposed. To this end it isnecessary that the negatives used to expose the lithographic plate be inprecise register and proper contact. While devices of this generalcharacter are known, because of the extremely accurate machine workrequired the fabrication thereof, and the large bulk and weightinvolved, such devices are relatively costly, and the use thereof isconsequently restricted. In addition, the systems employed in prior artmachines are complicated and require considerable training before theoperator is capable of reproducing satisfactory work.

In my prior above mentioned US. Pat. No. 3,150,582 there is disclosed adevice including a generally vertically oriented frame which supports anegative carrier in such manner that it may be moved in a parallelvertical plane over the face of a support for the lithographic film, andbe locked in proper position in any one of a plurality of positionswhereby successive exposures may be made. By virtue of cooperating racksarranged along vertical and horizontal axes, it is possible to obtainfine adjustment of the order of one half of a single rack tooth ineither of the two above mentioned directions fore the negative carrieris locked in position just prior to an exposure. While this adjustmentis simple to use, and has found considerable acceptance in thelithographing trade, it is sometimes desirable to have even fineradjustment of the order of several thousandths of an inch, which thetoothed rack engagement cannot always provide,

It is therefore among the principal objects of the present invention toprovide improved fine adjustment means which may be employed in a mannerto supplement coarser adjustments of the toothed rack type, whereby thebest features of both types of adjustment may be simultaneouslyutilized.

Another object of the invention lies in the incorporation of improvednegative cooling means for use during exposure of the negative injuxtaposition to a sheet of photolithographic film, so that withsuccessive exposures under the action of relatively hot illuminationlamp means, the temperature of the negative film being printed ismaintained within satisfactory limits.

Yet another object of the invention lies in the provision of improvedfine adjustment means of the class described which may be readilyincorporated into existing prior art devices without extensivemodification, and at correspondingly low cost.

A further object of the invention lies in the provision of improvednegative cooling means as above described which may be also incorporatedinto existing prior art devices with relatively small modification andcost.

These objects and features, as well as other incidental ends andadvantages, will more fully appear in the progress of the followingdisclosure, and be pointed out in the appended claims.

ln the drawings, to which reference will be made in the specification,similar reference characters have been employed to designatecorresponding parts throughout the several views. FIG. 1 is a frontperspective view of an embodiment of the invention.

FIG. 2 is a fragmentary view in perspective, corresponding to that seenin FIG. 1, and showing certain of the component parts in alteredrelative position.

FIG. 3 is a fragmentary enlarged vertical sectional view as seen fromthe plane 3-3 in FIG. 1.

FIG. 4 is a vertical fragmentary sectional view as seen from the plane4-4 in FIG. 5.

FIG. 5 is a fragmentary enlarged front elevational view of a chasesupport incorporating a horizontal axis adjustment means.

FIG. 6 is a fragmentary view in elevation showing a correspondingvertical axis adjustment means, with certain of the parts removed forpurposes of clarity.

FIG. 7 is a fragmentary view in elevation showing the structure removedfrom FIG. 6.

FIG. 8 is a fragmentary side elevational view as seen from the left-handportion of FIG. 6.

In accordance with the invention, the device, generally indicated byreference character 9 comprises broadly: a base 10, a lithographic platesupport element 11, lithographic plate registering means 12, mountingmeans 13 for positioning the support element 11, a negative carriersupport 14, horizontal registering means 15, vertical registering means16, and means 17 to vertically move the horizontal registering means.Supported from the frame 9 is a negative carrier illumination means 18.

The base 9 is preferably possessed of sufficient weight and rigidity toform a stable foundation for the device. Projecting perpendicularlyupwardly from the base are a pair of uprights I9 and 20. Secured betweenthe uprights I9 and 20 are a plurality of struts 21 forming the mountingmeans 13.

The vertical registering means 16 includes a pair of racks 23 and 24which are substantially identical and are in horizontal alignment.Slidably disposed on said racks are a pair of housings 25 and 26, and,as shown in FIG. 8, they may have rollers 27 which ride withincorresponding channels 28 (see FIG. I). Overlying the racks 23 and 24are short rack sections 29 which are completely complementary to theracks, so that with relatively light pressure the rack sections willproperly and alignedly seat or mesh with the racks to immobilize thehousings with respect thereto. The rack sections 29 are moved toward andaway from the racks 23 and 24 by structure shown in FIG. 8, and sincethe housings 25 and 26 are symmetrically identical, a detaileddescription of one will suffice for the other.

The rack sections 29 are pivotally mounted on a pin 30 trunnioned in heblock 3011, and are normally urged to disengaged position by coilsprings (not shown), there being one spring for each of the racksections. Each of the rack sections 29 acts as a follow for itsrespective cam roller 31 or 32 which are interconnected, and providedwith a vertical shift lever 33 keyed to a horizontal shaft 34 joumaledin bearings 35. The bearings 35 are secured, one each, to the housings25 and 26. When the lever 33 is in its upward position as shown in FIG.8, one of the rack sections 29 is engaged with a rack 23-24, and whenthe lever 33 is in its downward position, as shown in FIG. 6, the otherrack section 29 is engaged with a rack 23-24. As the two adjacent racksections are ofi'set by a fine interval, approximately one-half toothpitch, depending upon whether the lever 33 is moved upwardly ordownwardly, and the fineness of the tooth pitch, adjustments in theorder of one-sixteenth of an inch may be obtained in the above describedmanner.

Thus, the means 16 serves to provide a relatively coarse adjustment invertical displacement of the negative carrier support 14 throughvertical movement of the housings 25 and 26 as joined by the transversemember 37. The housings 25 and 26 are connected to one point on annularchains 38 and 39 which ride on upper sprockets 40 and 41 and lowersprockets 42 and 43. A counterweight (not shown) in mounted on thechains 38-39 to substantially offset the weight of the means 16. Theupper sprockets 40 and 41 are fixed on a transverse upper shaft 45joumaled on he ends of the uprights 19 and 20, respectively. One end ofthe shaft 45 is connected by a pair of bevel gears (not shown) to avertical shaft 47 and hand-wheel 48. Thus, when the shift lever 33 is inits neutral position, wherein both rack sections 29 are disengaged,rotation of the hand-wheel moves the transverse member and housings upor down to a desired approximate position (as for example to a positionwithin one-eighth inch of the ultimately desired posi' tion). Moving theshift lever up or down will then force one or the other of the racksections into the racks, and when the arts are fully interengaged theywill be disposed precisely at a predetermined position within the stepswhich are equal to half the pitch of the racks.

To obtain still closer adjustment, in the order of the nearest onethousandth of an inch, the housings 25 and 26 include auxiliary frameelements 49 arranged for rectilinear movement with respect thereto. Eachauxiliary frame element includes a plurality of frame members 50, 51, 52and 53 (see FIG. 6), the same supporting a pair of trunnions 54 and 55which inturn mount a stub shaft 56. The shaft 56 mounts a smallhand-wheel or knob 57 at one end, and a threaded collar 58 movement isan opposite end which shaft a transverse shaft 59 to transmit motion toa corresponding shaft the transverse shown) on the oppositely disposedhousing. The stub shaft 56 mounts a bevel gear 60 which transmits motionto a adjustment. gear 61 on a vertically arranged internally threadedbushing 62. A threaded shaft 63 engages the bushing 62 and is providedwith a nut member 64 mounted within a supporting bracket 65. The bracket65 supports a transverse member 66 to be described in greater detailhereinafter. It also supports an index member 67 alignable with an indexmark 68 on the frame member 50 when the nut member 64 is in a mediallocation. The racket 65 also mounts a dial-type micrometer gauge 70, theoperating mechanism of which cooperates with a stud 71 on the framemember 53. From a consideration of FIGS. 6, 7 and 8, it will be apparentthat when the housings 25 and 26 are in locked relation with respect tohe racks 23 and 24, rotation of the knob 57 results in rotation of thebushing 62, and the raising or lowering of the nut member 64 and bracket65. This movement is transmitted through the transverse shaft 59 toresult in corresponding movement at the other side of the transversebeam 66, so that the beam 66 moves upwardly or downwardly in ahorizontal plane the requisite degree of adjustment. This adjustmentwill normally be less than the degree of adjustment obtainable byengagement of the rack sections with the racks, and as indicated in FIG.7 may be as much as .050 inch in either direction. Because of theextremely high mechanical advantage involved, no locking means isnonnally required for the above described adjustment.

The horizontal registering means includes a rectangularly shaped member75 (see FIGS. 4and 5) supported on he transverse beam 66 by rollers 76.Corresponding to similar structure in the vertical registering means 16,there are provided rack sections 78 each of which selectively engagesthe rack 79 on the transverse beam 66. The rack sections 78 are mountedon a pin 80 which provides a pivotal axis in a member 81 which remainsfixed with respect to the rack 79 when either rack section is engagedtherewith. A pair of corresponding cam rollers, one of which isindicated by reference character 82 are both mounted on a pivotallymounted cam member 83 operated by a shift lever 84. A horizontallyadjustable plate 85 is supported in position between upper and lowerguides 86 and 87 respectively, the plate being formed integrally withthe member 81, and mounting an eccentric cam 88 on a shaft 90. The camincludes a manually engageable member 89 for rotation thereof, theeccentric cam surface bearing against the surface of a circular bore ina follower plate integral with the member 75. Thus, with rotation of thecam 88, minute adjustment of the member 75 along the transverse beam 66is possible. A micrometer gauge 92 is connected to an operating pintle93, and is fixed with respect to the member 81, so as to indicatemovement of the member 75. A locknut 95 bears down upon the shaft 90,and prevents rotation in those applications where minute horizontaladjustment is not required. The nut is provided with a manuallyengageable member 96 extending therethrough to facilitate loosening andtightening thereof. The negative carrier support 14 is secured to thelower portion of the member 75, and thus moves horizontally therewith.From a consideration of FIGS. 4 and 5, it will be apparent that a simplemode of operation includes the locating of the member 75 first bylocking the same using the shift lever 84, and the subsequent rotationof he cam 88 while reading horizontal displacement on the gauge 92 to heprecision desired.

Referring again to FIG. 6 in the drawings, the transverse beam 66 isprovided with a horizontally arranged groove or track 97 in which thereis slidably disposed an elongated scale member 98. Preferably, the track98 is of rectangular cross section, including an upper wall 99 and alower wall 100 provided with a plurality of small vertically orlaterally arranged bores 101 spaced from each other in equal increments,as for example 1 inch intervals. The leftward end of the scale member 98is provided with a pivotal locking member 103 mounted on a pintle 104,and having a projection 105 selectively engageable in one of the bores101. Rightwardly of the pintle 104 is an index (a point of zeromeasurement) 106, and subsequent graduations 107. Extending-leftwardlyfrom the member 75 is a corresponding index member 108 alignable withthe graduations 107.

While the scale member 98 will normally be positioned with the pintle104 engaged in the leftwardmost bore 101, in certain types of copy, itmay be desirable to arrange the leftward margin inwardly from the normalleftward edge of the plate support element 11. When such is the case,the locking member 103 is manually pivoted out of engagement with theleftwardmost bore 101, and the scale member 98 slid rightwardly to hedesired location following which the locking member 103 is again engagedwithin another bore 101. With a new reference point established, themember 75 maybe moved with relation thereto without the necessity ofmaking mental additions to each measurement made on the scale member 98.

Referring to FIGS. 1, 2 and 3, the negative carrier illumina' tion means118 is mounted on upper and lower horizontal guides 111 and 112,respectively, the guides in turn supporting a vertical stanchion 113.Extending forwardly of the stanchion 113 and mounted at its upper andlower ends thereto is a vertical supporting shaft 114 mounting a slidingbracket 115. A cable 116 interconnects the upper portion of the bracketand passes over a pulley 117 to a counterweighting means (not shown)disposed within the stanchion 113. A hinge connection 118 supports alamp-housing 119 in which there is disposed a suitable Xenon-typeilluminating tube, as well as suitable cooling means 120. The housing119 includes a flared hood 121 in which the Xenon tube is disposed atapered hood 122, the rectangular free edge 123 of which corresponds indimension to a recess 124 in the negative carrier 125.

At the narrow end 127 of the tapered hood 122 is a peripheral wall 128which defines the edge 123. Positioned within the wall 128 is an airinlet means 131 which provides a cooling flow of air across the face ofthe negative support without permitting the leakage of light from theXenon tube from the lamp-housing 119. The means 131 includes a firstwall member 132 having first and second mutually angularly disposed wallportions 133 and 134 as well as a second wall member 135 having mutuallyangularly disposed wall portions 136 and 137. The wall member 132 and135 thus define a continuous passage for the flow of air, including aninlet portion 138 and an outlet portion 139 positioned adjacent theperipheral edges of the glass frame 140 normally in direct contact witha negative disposed therebeneath. Thus, air entering the lamp-housing119 in flowing to the cooling means 120 will form a curtain of cool airbetween the lamp tube and he negative which will permit constant heatremoval by convection so that repeated exposures of the same negative atdifferent portions of the area of the photolithographic plate will stillmaintain the temperature of the negative at an acceptably low level.

I wish it to be understood that I do not consider the invention limitedto the precise details of structure shown and set forth in thisspecification, for obvious modifications will occur to those skilled inthe art to which the invention pertains.

lclaim:

1. In a photo-offset platemaking machine, including a negative carrierand a negative carrier illumination means supported for movement elativeto said negative carrier, the improvement comprising: said negativecarrier including a planar surface surrounding a negative carriedthereby, said negative carrier illumination means including a hoodhaving a continuous edge defining an opening selectively abuttableagainst said planar surface of said negative carrier to form alightproof seal; said hood having a peripherally disposed continuouslight trap ventilating means adjacent said continuous edge and coolingmeans interconnected with said hood at a point remote from saidventilating means; whereby, when said illumination means is placedagainst said planar surface of said negative carrier, light leakagetherebetween is prevented, and operation of said cooling means willcause air to flow over the surface of said negative carrier to form acurtain of moving air between said surface and heat impinging thereuponfrom said illumination means.

1. In a photo-offset platemaking machine, including a negative carrierand a negative carrier illumination means supported for movement elativeto said negative carrier, the improvement comprising: said negativecarrier including a planar surface surrounding a negative carriedthereby, said negative carrier illumination means including a hoodhaving a continuous edge defining an opening selectively abuttableagainst said planar surface of said negative carrier to form alightproof seal; said hood having a peripherally disposed continuouslight trap ventilating means adjacent said continuous edge and coolingmeans interconnected with said hood at a point remote from saidventilating means; whereby, when said illumination means is placedagainst said planar surface of said negative carrier, light leakagetherebetween is prevented, and operation of said cooling means willcause air to flow over the surface of said negative carrier to form acurtain of moving air between said surface and heat impinging thereuponfrom said illumination means.